| 1. |
- Pashazadehgaznagh, Sajjad, 1994, et al.
(författare)
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An Intriguing Array of Extrudate Patterns in Long-Chain Branched Polymers During Extrusion
- 2023
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Ingår i: Macromolecular Materials and Engineering. - 1439-2054 .- 1438-7492. ; 308:8
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Tidskriftsartikel (refereegranskat)abstract
- The present study highlights a range of surface and volume extrudate patterns that can be detected during the extrusion flow of long-chain branched polymers. Thus, four linear low-density polyethylenes (LDPEs) have been extruded using a single-screw extruder coupled to an inline optical imaging system. The selected LDPEs are selected to outline the influence of molecular weight and long-chain branching on the types of melt flow extrusion instabilities (MFEI). Through the inline imaging system, space–time diagrams are constructed and analyzed via Fourier-transformation using a custom moving window procedure. Based on the number of characteristic frequencies, peak broadness, and whether they are surface or volume distortions, three main MFEI types, distinct from those typically observed in linear and short-chain branched polymers, are identified. The higher molecular weight, low long-chain branching LDPEs exhibited all three instability types, including a special type volume instability. Independently of the molecular weight, higher long-chain branching appeared to have a stabilizing effect on the transition sequences by suppressing volume extrudate distortions or limiting surface patters to a form of weak intensity type.
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| 2. |
- Pashazadehgaznagh, Sajjad, 1994, et al.
(författare)
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Mapping surface defects in highly-filled wood fiber polymer composite extrusion from inline spectral analysis
- 2023
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Ingår i: Composites Science and Technology. - 0266-3538. ; 242
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Tidskriftsartikel (refereegranskat)abstract
- Surface defects in highly-filled wood polymer composites (WPCs) are mapped in single-screw extrusion via inline optical spectral analysis for the first time. The effects of wood fiber content and drying on the dynamics of surface defects are spatio-temporally resolved via space–time inline optical imaging. Surface tearing appeared from the lowest shear rates investigated followed by a gradual decay in spectral intensity with increasing shear rates/slip velocities. This is accompanied by broadening of the surface tearing characteristic frequency while the average wavelength is estimated to remain constant within the experimental conditions. Increasing shear rates, drying and increasing wood fiber content showed mitigating effects on surface tearing. However, surface tearing in undried samples was still present even at the highest shear rates and high wall slip velocities. A regime where the extrudate surface is dominated by bubbles at high shear rates and low wood fiber contents in undried WPCs was identified.
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| 3. |
- Rahimi, Shadi, 1982, et al.
(författare)
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Automated Prediction of Bacterial Exclusion Areas on SEM Images of Graphene–Polymer Composites
- 2023
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Ingår i: Nanomaterials. - 2079-4991. ; 13:10
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Tidskriftsartikel (refereegranskat)abstract
- To counter the rising threat of bacterial infections in the post-antibiotic age, intensive efforts are invested in engineering new materials with antibacterial properties. The key bottleneck in this initiative is the speed of evaluation of the antibacterial potential of new materials. To overcome this, we developed an automated pipeline for the prediction of antibacterial potential based on scanning electron microscopy images of engineered surfaces. We developed polymer composites containing graphite-oriented nanoplatelets (GNPs). The key property that the algorithm needs to consider is the density of sharp exposed edges of GNPs that kill bacteria on contact. The surface area of these sharp exposed edges of GNPs, accessible to bacteria, needs to be inferior to the diameter of a typical bacterial cell. To test this assumption, we prepared several composites with variable distribution of exposed edges of GNP. For each of them, the percentage of bacterial exclusion area was predicted by our algorithm and validated experimentally by measuring the loss of viability of the opportunistic pathogen Staphylococcus epidermidis. We observed a remarkable linear correlation between predicted bacterial exclusion area and measured loss of viability (R2 = 0.95). The algorithm parameters we used are not generally applicable to any antibacterial surface. For each surface, key mechanistic parameters must be defined for successful prediction.
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| 4. |
- Ruan, Hengzhi, 1995, et al.
(författare)
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Biomimetic Antibacterial Gelatin Hydrogels with Multifunctional Properties for Biomedical Applications
- 2023
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Ingår i: ACS Applied Materials & Interfaces. - 1944-8252 .- 1944-8244. ; 15:47, s. 54249-54249–54265
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Tidskriftsartikel (refereegranskat)abstract
- A facile novel approach of introducing dopamine and [2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide via dopamine-triggered in situ synthesis into gelatin hydrogels in the presence of ZnSO4 is presented in this study. Remarkably, the resulting hydrogels showed 99.99 and 100% antibacterial efficiency against Gram-positive and Gram-negative bacteria, respectively, making them the highest performing surfaces in their class. Furthermore, the hydrogels showed adhesive properties, self-healing ability, antifreeze properties, electrical conductivity, fatigue resistance, and mechanical stability from −100 to 80 °C. The added multifunctional performance overcomes several disadvantages of gelatin-based hydrogels such as poor mechanical properties and limited thermostability. Overall, the newly developed hydrogels show significant potential for numerous biomedical applications, such as wearable monitoring sensors and antibacterial coatings.
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| 5. |
- Ruan, Hengzhi, 1995, et al.
(författare)
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Polysaccharide-based antibacterial coating technologies
- 2023
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Ingår i: Acta Biomaterialia. - 1878-7568 .- 1742-7061. ; 168, s. 42-77
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Forskningsöversikt (refereegranskat)abstract
- To tackle antimicrobial resistance, a global threat identified by the United Nations, is a common cause of healthcare-associated infections (HAI) and is responsible for significant costs on healthcare systems, a substantial amount of research has been devoted to developing polysaccharide-based strategies that prevent bacterial attachment and biofilm formation on surfaces. Polysaccharides are essential building blocks for life and an abundant renewable resource that have attracted much attention due to their intrinsic remarkable biological potential antibacterial activities. If converted into efficient antibacterial coatings that could be applied to a broad range of surfaces and applications, polysaccharide-based coatings could have a significant potential global impact. However, the ultimate success of polysaccharide-based antibacterial materials will be determined by their potential for use in manufacturing processes that are scalable, versatile, and affordable. Therefore, in this review we focus on recent advances in polysaccharide-based antibacterial coatings from the perspective of fabrication methods. We first provide an overview of strategies for designing polysaccharide-based antimicrobial formulations and methods to assess the antibacterial properties of coatings. Recent advances on manufacturing polysaccharide-based coatings using some of the most common polysaccharides and fabrication methods are then detailed, followed by a critical comparative overview of associated challenges and opportunities for future developments. Statement of significance: Our review presents a timely perspective by being the first review in the field to focus on advances on polysaccharide-based antibacterial coatings from the perspective of fabrication methods along with an overview of strategies for designing polysaccharide-based antimicrobial formulations, methods to assess the antibacterial properties of coatings as well as a critical comparative overview of associated challenges and opportunities for future developments. Meanwhile this work is specifically targeted at an audience focused on featuring critical information and guidelines for developing polysaccharide-based coatings. Including such a complementary work in the journal could lead to further developments on polysaccharide antibacterial applications.
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